Square-Pyramidal/Triangular Framework Oxide:  Synthesis and Structure of PKU-6

PKU-6, a new aluminoborate (HAl2B3O8), has been synthesized in a closed system at 400 °C. The structure of PKU-6, characterized by using powder and single-crystal X-ray diffraction, consists of AlO5 square-pyramidal chains and B3O7 groups, which are interconnected and form a three-dimensional framework. The 27Al NMR study indicates that the isotropic chemical shift of pyramidal Al is 34.6 ppm with a large quadrupolar coupling constant (CQ = 4.2 MHz), mainly due to a nonspherical coordination environment.